The lens of the eye is a biconvex transparent structure that helps to focus light onto the retina, where mature fiber cells of the lens contain high amounts of protein and are important for the transparency and refractive power of the lens. Normally, these proteins are protected from oxidation by reducing substances and by the low-oxygen environment around the lens. Indeed, within the eye, oxygen concentration decreases sharply from the retina towards the lens due to the presence of the vitreous gel. As such, surgical removal or involutional degeneration of the vitreous gel often increases the exposure of the lens to oxygen originating from the retinal vasculature.
Vitrectomy is the surgical method used to remove some or all of the vitreous gel from the eye. It is an essential step of many vitreoretinal surgical procedures and is performed on approximately 500,000 patients per year in the United States alone. However, removal of the vitreous often results in an efflux of oxygen inside the eye through diffusion from the retina-choroid complex and/or ion-assisted transport of oxygen through the vitreous gel. In addition, oxygen is also introduced through the surgical incisions and gases or solutions used to temporarily replace the vitreous gel. As a result, nearly half of patients develop secondary cataracts within two years after undergoing a vitrectomy due to increased intraocular oxygen levels.
Current practices after vitrectomy to reduce the risk of cataract formation include requiring patients to maintain tedious head-down positions to keep the gas bubbles away from the lens until the bubbles are completely absorbed. Unfortunately, maintaining a head-down position for a prolonged time is often highly challenging, especially among the elderly, and may have several side-effects, such as ulnar nerve pinching. Thus, half of the patients facing these requirements after vitrectomy are ultimately not compliant. Nevertheless, there is currently no other medical or surgical method effective to prevent the onset of post-vitrectomy cataracts.
Accordingly, there remains a need for a composition and/or method that can maintain low oxygen pressure around the eye lens to prevent oxidative damage and the formation of lens opacities, but that is also biocompatible, does not require invasive surgery, and does not unduly compromise a subject's vision.